Unverified Commit 0c0effb0 authored by Mickaël Salaün's avatar Mickaël Salaün
Browse files

landlock: Refactor filesystem access mask management 



Replace get_raw_handled_fs_accesses() with a generic
landlock_union_access_masks(), and replace get_fs_domain() with a
generic landlock_get_applicable_domain().  These helpers will also be
useful for other types of access.

Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
Reviewed-by: default avatarGünther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20241109110856.222842-2-mic@digikod.net


[mic: Slightly improve doc as suggested by Günther]
Signed-off-by: default avatarMickaël Salaün <mic@digikod.net>
parent 53b9d789

security/landlock/fs.c

+8 −23
Original line number Diff line number Diff line
@@ -388,38 +388,22 @@ static bool is_nouser_or_private(const struct dentry *dentry) 
		unlikely(IS_PRIVATE(d_backing_inode(dentry))));

}



static access_mask_t

get_raw_handled_fs_accesses(const struct landlock_ruleset *const domain)

{

	access_mask_t access_dom = 0;

	size_t layer_level;



	for (layer_level = 0; layer_level < domain->num_layers; layer_level++)

		access_dom |=

			landlock_get_raw_fs_access_mask(domain, layer_level);

	return access_dom;

}



static access_mask_t

get_handled_fs_accesses(const struct landlock_ruleset *const domain)

{

	/* Handles all initially denied by default access rights. */

	return get_raw_handled_fs_accesses(domain) |

	return landlock_union_access_masks(domain).fs |

	       LANDLOCK_ACCESS_FS_INITIALLY_DENIED;

}



static const struct landlock_ruleset *

get_fs_domain(const struct landlock_ruleset *const domain)

{

	if (!domain || !get_raw_handled_fs_accesses(domain))

		return NULL;



	return domain;

}

static const struct access_masks any_fs = {

	.fs = ~0,

};



static const struct landlock_ruleset *get_current_fs_domain(void)

{

	return get_fs_domain(landlock_get_current_domain());

	return landlock_get_applicable_domain(landlock_get_current_domain(),

					      any_fs);

}



/*
@@ -1517,7 +1501,8 @@ static int hook_file_open(struct file *const file) 
	access_mask_t open_access_request, full_access_request, allowed_access,

		optional_access;

	const struct landlock_ruleset *const dom =

		get_fs_domain(landlock_cred(file->f_cred)->domain);

		landlock_get_applicable_domain(

			landlock_cred(file->f_cred)->domain, any_fs);



	if (!dom)

		return 0;

security/landlock/ruleset.h

+66 −8
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 


#include <linux/bitops.h>

#include <linux/build_bug.h>

#include <linux/kernel.h>

#include <linux/mutex.h>

#include <linux/rbtree.h>

#include <linux/refcount.h>
@@ -47,6 +48,15 @@ struct access_masks { 
	access_mask_t scope : LANDLOCK_NUM_SCOPE;

};



union access_masks_all {

	struct access_masks masks;

	u32 all;

};



/* Makes sure all fields are covered. */

static_assert(sizeof(typeof_member(union access_masks_all, masks)) ==

	      sizeof(typeof_member(union access_masks_all, all)));



typedef u16 layer_mask_t;

/* Makes sure all layers can be checked. */

static_assert(BITS_PER_TYPE(layer_mask_t) >= LANDLOCK_MAX_NUM_LAYERS);
@@ -260,6 +270,61 @@ static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset) 
		refcount_inc(&ruleset->usage);

}



/**

 * landlock_union_access_masks - Return all access rights handled in the

 *				 domain

 *

 * @domain: Landlock ruleset (used as a domain)

 *

 * Returns: an access_masks result of the OR of all the domain's access masks.

 */

static inline struct access_masks

landlock_union_access_masks(const struct landlock_ruleset *const domain)

{

	union access_masks_all matches = {};

	size_t layer_level;



	for (layer_level = 0; layer_level < domain->num_layers; layer_level++) {

		union access_masks_all layer = {

			.masks = domain->access_masks[layer_level],

		};



		matches.all |= layer.all;

	}



	return matches.masks;

}



/**

 * landlock_get_applicable_domain - Return @domain if it applies to (handles)

 *				    at least one of the access rights specified

 *				    in @masks

 *

 * @domain: Landlock ruleset (used as a domain)

 * @masks: access masks

 *

 * Returns: @domain if any access rights specified in @masks is handled, or

 * NULL otherwise.

 */

static inline const struct landlock_ruleset *

landlock_get_applicable_domain(const struct landlock_ruleset *const domain,

			       const struct access_masks masks)

{

	const union access_masks_all masks_all = {

		.masks = masks,

	};

	union access_masks_all merge = {};



	if (!domain)

		return NULL;



	merge.masks = landlock_union_access_masks(domain);

	if (merge.all & masks_all.all)

		return domain;



	return NULL;

}



static inline void

landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset,

			    const access_mask_t fs_access_mask,
@@ -295,19 +360,12 @@ landlock_add_scope_mask(struct landlock_ruleset *const ruleset, 
	ruleset->access_masks[layer_level].scope |= mask;

}



static inline access_mask_t

landlock_get_raw_fs_access_mask(const struct landlock_ruleset *const ruleset,

				const u16 layer_level)

{

	return ruleset->access_masks[layer_level].fs;

}



static inline access_mask_t

landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,

			    const u16 layer_level)

{

	/* Handles all initially denied by default access rights. */

	return landlock_get_raw_fs_access_mask(ruleset, layer_level) |

	return ruleset->access_masks[layer_level].fs |

	       LANDLOCK_ACCESS_FS_INITIALLY_DENIED;

}

security/landlock/syscalls.c

+1 −1
Original line number Diff line number Diff line
@@ -329,7 +329,7 @@ static int add_rule_path_beneath(struct landlock_ruleset *const ruleset, 
		return -ENOMSG;



	/* Checks that allowed_access matches the @ruleset constraints. */

	mask = landlock_get_raw_fs_access_mask(ruleset, 0);

	mask = ruleset->access_masks[0].fs;

	if ((path_beneath_attr.allowed_access | mask) != mask)

		return -EINVAL;